The invention relates to cyclonic separating apparatus. Particularly, but not exclusively, the invention relates to cyclonic separating apparatus for use in vacuum cleaners.
Cyclonic separating apparatus is well known and has uses in a wide variety of applications. Over the last decade or so, the use of cyclonic separating apparatus to separate particles from an airflow in a vacuum cleaner has been developed and introduced to the market. Detailed descriptions of cyclonic separating apparatus for use in vacuum cleaners are given in, inter alia, U.S. Pat. Nos. 3,425,192 and 4,373,228 and EP 0 042 723. From these and other prior art documents, it can be seen that it is known to provide two cyclone units in series so that the airflow passes sequentially through at least two cyclones. This allows the larger dirt and debris to be extracted from the airflow in the first cyclone, leaving the second cyclone to operate under optimum conditions and so effectively to remove very fine particles in an efficient manner. This type of arrangement has been found to be effective when dealing with airflows in which is entrained a variety of matter having a wide particle size distribution. Such is the case in vacuum cleaners.
It is also desirable for vacuum cleaners to be both compact and energy efficient. A further desirable feature is a large capacity for collecting dirt and debris to reduce the frequency of emptying. In some known arrangements, the downstream cyclone has been placed inside the upstream cyclone in an attempt to minimize the size of the cleaner (see, for example, U.S. Pat. No. 4,373,228 and EP 0 042 723). However, this reduces the capacity of the cleaner because the downstream cyclone occupies a space which would otherwise be available for dirt and dust collection. In arrangements of the type shown in U.S. Pat. No. 3,425,192, the downstream cyclones are located outside the upstream cyclone but the partially cleaned air exiting from the upstream cyclone must then travel some distance to the inlets of the downstream cyclones. This increases the pressure drop across the system as a whole and thus reduces the energy efficiency of the system. Furthermore, the volume of the means for conducting the partially cleaned air adds to the overall volume of the machine.
The present invention provides a cyclonic separating apparatus which has an improved capacity for collecting separated particles and an improved energy efficiency. The invention also provides a cyclonic separating apparatus suitable for use in vacuum cleaners and capable of achieving improved performance compared to the prior art. Another feature of the invention is to provide a cyclonic separating apparatus capable of mitigating the disadvantages of the prior art.
The invention provides a cyclonic separating apparatus that includes an upstream cyclone unit and a downstream cyclone unit. The upstream cyclone unit includes at least one cyclone having a first end and a second end, and the downstream cyclone unit includes at least one cyclone having a first end and a second end, with the upstream and downstream cyclone units arranged relative to one another so that the orientation of at least one cyclone of the downstream cyclone unit is substantially inverted with respect to the orientation of at least one cyclone of the upstream cyclone unit.
The inversion of the downstream cyclone unit with respect to the upstream cyclone unit allows the cyclone units to be arranged in a manner which reduces the length of the airflow path between the upstream cyclone unit and the downstream cyclone unit, particularly when the downstream cyclone unit is located outside the upstream cyclone unit. This means that the pressure drop across the entire apparatus can be kept to a minimum, thereby increasing the energy efficiency of the apparatus, while the collecting capacity of the apparatus is maintained as high as possible.
In a preferred embodiment, the downstream cyclone unit is located outside the upstream cyclone unit, and both cyclone units are arranged substantially vertically with the first end of one or more cyclones of the upstream cyclone unit uppermost and the first end of one or more cyclones of the downstream cyclone unit lowermost. Thus, the outlet or outlets of the cyclones of the upstream cyclone unit are located close to the inlets of the cyclone or cyclones of the downstream cyclone unit. This ensures that the length of the airflow path between the cyclone units is minimized so that losses are kept to a minimum. The second ends of one or more cyclones of the downstream cyclone unit project away from the upstream cyclone unit rather than being located inside the upstream cyclone unit. This maximizes the capacity of the upstream cyclone unit for collecting dirt and debris and thus reduces the frequency with which the upstream cyclone unit requires emptying.
A preferred feature of the aforementioned embodiment is that the cyclones of the downstream cyclone unit are inclined with respect to one another so that the said cyclones approach one another at the second ends thereof. This arrangement discourages deposition of separated fine dirt and dust on the outer surfaces of the cyclones of the upstream cyclone unit.
It is preferred that the apparatus according to the invention is incorporated into a vacuum cleaner, preferably a domestic vacuum cleaner. This is because the combined advantages of increased collecting capacity and reduced pressure drop are particularly useful in a vacuum cleaner. The user sees the benefits of reduced power consumption and less frequent emptying procedures.
Other preferred features are set out in the description below, the claims and the appended drawings.